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Why is newborn screening important for phenylketonuria?

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BRCA2 tumor suppressor gene on chromosome 13 — human genetic disease Photomicrograph of the *BRCA2* tumor suppressor gene on chromosome 13 of the human genome. Inactivation of this growth-regulating gene is associated with a higher risk of developing breast cancer.

Newborn screening for phenylketonuria (PKU) is critical because it allows for the early detection and management of this inborn error of metabolism before irreversible damage occurs.12

In individuals with PKU, the body lacks the enzyme phenylalanine hydroxylase, which is necessary to convert the amino acid phenylalanine into tyrosine. Without this conversion, phenylalanine accumulates to toxic levels, which interferes with nervous system function and leads to severe, progressive symptoms such as intellectual disability, seizures, and behavioral abnormalities.34

Because these symptoms can become apparent within months of birth, screening—typically performed via a simple blood test shortly after birth—is essential. Early identification enables the immediate implementation of a strict, low-phenylalanine diet. When this dietary intervention is started early and maintained, it effectively prevents brain damage, allowing children with PKU to grow into healthy adults who can lead full and productive lives.3124